Pressure-exchange assisted closed circuit desalination systems for continuous desalination of low energy and high recovery under fixed flow and variable pressure conditions

Abstract

The inventive system and method comprises one or more batch closed circuit desalination (CCD) unit(s) linked by conducting lines and valves means to a pressure exchange (PE) means, such that each said CCD can be engaged periodically with said PE means for brine replacement by fresh pressurized feed, thereby, enable a continuous consecutive sequential batch desalination under fixed flow and variable pressure conditions of low energy and high recovery of unchanged flux. The inventive system and method opens the door to large scale CCD systems operated by predetermined fixed set points of pressurized feed low, cross-flow or module recovery, and system recovery, independent of each other, of infinite operational combinations and high flexibility for effective process optimization. The inventive system and method overcome former volume requirement limitations of large scale SWRO CCD installations.

Claims

1. A system for treating a feed solution by closed circuit desalination, said system comprising: a module containing a selected number of membrane elements and comprising a module inlet, a first module outlet for discharging a pressurized concentrate stream, and a second module outlet for discharging a permeate stream to a permeate outlet line; a closed circuit line connecting said first module outlet and said module inlet, said closed circuit line suitable to convey the discharged pressurized concentrate stream from said first module outlet to said module inlet; a recirculation pump located within the closed circuit line, said recirculation pump having a variable frequency drive; a high-pressure pump (HP) comprising a HP inlet for receiving the feed solution from a first path and a HP outlet for providing a pressurized feed solution to the closed circuit line; a pressure exchange unit (PE) comprising: a first PE inlet for receiving the feed solution from a second path; a first PE outlet suitable for providing a pressurized feed solution to the closed circuit line at a first junction point within the closed circuit line; a second PE inlet suitable for receiving the pressurized concentrate stream from a second junction point within the closed circuit line, said second junction point is located between the first junction point and the first module outlet; a second PE outlet for providing a depressurized concentrate stream to a brine effluent line; a plurality of valves suitable to be configured in a first mode of operation wherein flow is enabled to pass between the second junction point and the first junction point, and the pressurized concentrate stream discharged from the first module outlet is mixed with the pressurized feed solution from the high-pressure pump and conveyed to the module inlet; and suitable to be configured in a second mode of operation wherein flow is prevented between the second junction point and the first junction point, and the pressurized concentrate stream discharged from the first module outlet is passed through the second junction point, the second PE inlet, the second PE outlet, and into the brine effluent line, and feed solution passes from the second path through the first PE inlet, the first PE out, the first junction point, and into the closed circuit line; and a control system suitable to alternate between the first and second modes of operation.

2. The system for treating a feed solution by closed circuit desalination of claim 1, wherein a first loop comprises the module, the closed circuit line, and the recirculation pump, further wherein the system further includes a second loop comprising: a second module containing a selected number of membrane elements and comprising a second module inlet, a third module outlet for discharging a second pressurized concentrate stream, and a fourth module outlet for discharging a second permeate stream to a second permeate outlet line; a second closed circuit line connecting said third module outlet and said second module inlet, said second closed circuit line suitable to convey the second pressurized concentrate stream from said third module outlet to said second module inlet; and a second recirculation pump located within the second closed circuit line, said second recirculation pump having a variable frequency drive; wherein the first PE outlet is further suitable for providing pressurized feed solution to the second loop at a third junction point located within the second closed circuit line; and the second PE inlet is further suitable for receiving the second pressurized concentrate stream from a fourth junction point located within the second closed circuit line; said first mode of operation is further characterized by: preventing flow between the fourth junction point and the third junction point; and enabling the second pressurized concentrate stream to pass through the fourth junction point, the second PE inlet, the second PE outlet, and into the brine effluent line; and said second mode of operation is further characterized by: enabling the second pressurized concentrate stream to pass between the fourth junction point and the third junction point.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1A: A schematic diagram of an inventive system for continuous closed circuit desalination comprising a batch CCD unit, a pressure exchange (PE) unit, and conducting lines and valve means between CCD and PE, showing an actuation mode where both said units are disengaged.

(2) FIG. 1B: A schematic diagram of an inventive system for continuous closed circuit desalination comprising a batch CCD unit, a pressure exchange (PE) unit, and conducting lines and valve means between CCD and PE, showing an actuation mode where both said units are engaged.

(3) FIG. 2: A schematic diagram of the inventive system for continuous closed circuit desalination comprising a batch CCD unit, a pressure exchange (PE) unit, conducting lines and valve means between CCD and PE during an engagement mode, and RO skids of different plausible configurations such as NNEn [A], N(2MEn) [B] and, N(3MEn) [C], where MEn stands for a module containing and n elements and N for vertically fed of one. two and three horizontally linked modules, respectively.

(4) FIG. 3: A schematic diagram of multitude pressure exchange (PE) units with their inlets and outlets lines connected in parallel to enable their simultaneous actuation.

(5) FIG. 4: A schematic diagram of the inventive system for continuous closed circuit desalination comprising two batch CCD units, pressure exchange (PE) units, and the conducting lines and valve means between them. showing an actuation mode where one of the CCD units (RO-1) is disengaged from the PE means while the other unit (RO-2) is engaged with said PE means undergoing brine replacement with fresh feed, whereby continuous operation of both CCD units under fixed flow and variable pressure conditions is enabled by the alternating engagement of said units the with the PE means.

(6) FIG. 5: A schematic diagram of the inventive system as in FIG. 4; except that both units are supplied with pressurized feed by the same high pressure pump (HP) and the fixed flow variable pressure operation within each CCD unit is created by means of their separate booster pumps (BP).

DETAILED DESCRIPTION OF THE INVENTION

(7) The inventive step of the present invention relates to the use of PE means for brine replacement with fresh pressurized feed in batch CCD units operated consecutive sequentially under fixed flow and variable pressure conditions. Prior art leaching of brine replacement with fresh pressurized feed in said consecutive sequential batch CCD process through a disengaged/engaged single container (CCD-SC) proceeds with negligible hydrostatic compression/decompression energy losses with theory predicted near absolute energy conversion efficiency which was ultimately confirmed experimentally. PE means comprise mechanical unit of two inlets and outlets wherein a pressurized effluent stream actuates a feed pressurizing device and the efficiency of such a unit depends on the inlet-outlet pressure difference of said effluent stream, the hydraulic efficiency of said feed pressurizing device, and the degree of mixing between said brine effluent and feed streams. Isobaric ERD based of positive displacement principles of conventional PFD plants (e.g., PX, DWEER, etc.) are noted for their high hydraulic efficiency (93%-96%); however, the overall energy conversion efficiency of said ERD should be only ˜90% or less if account is taken of their inlet-outlet pressure-difference, mixing, and plausibly mechanical and flow induced pressure losses. Accordingly, the integration of the relatively small size PE means. such as the isobaric-ERD tools, into batch CCD units of fixed flow and variable pressure operational mode should enable a design flexibility of large production cost effective units by circumventing the need for large volume side containers; however, this will be done at an expense of a somewhat greater SE (˜10%) compared with that of CCD with a side container (CCD-SC). For example, the energy consumption projection of the inventive method (CCD-PE) for large scale Ocean seawater (35,000 ppm) desalination of 50% recovery at 13 lmh of ˜1.92 kWh/m.sup.3 is expected to be 10% higher than that demonstrated for a small scale CCD-SC unit (1.75 kWh/mW) and ˜22% lower than that of the most efficient SWRO-PX large commercial plant (2.45 kWh/m.sup.3l) located in Partt (Australia).

(8) An integrated system of a batch CCD unit for fixed flow and variable pressure operation with PE means according to one of the preferred embodiments of the inventive system disclosed schematically in FIG. 1 (AB), shows a single batch CCD unit, a single PE unit, conducting lines in each of said units and those between them, and the valve means and monitoring means whereby said system is actuated continuously under the designated flow and pressure conditions with performance continuously monitored to enable a process control and detection of male functions if occurred. The conducting lines in the drawing are distinguished from each other to facilitate the distinction of their function, with flow direction in lines indicated by arrows. The two-mode actuation of the inventive system; wherein, said CCD and PE units are either disengaged or engaged, are displayed in FIG. 1A and FIG. 18, respectively. The batch CCD unit in FIG. 1(AB) comprises a RO skid of a single module with a selected number of membrane elements, or of multitude of such modules with their respective inlet and outlet lines connected in parallel; a closed circuit line for concentrate recycling from outlet(s) to inlet(s) of said module(s) by means of a circulation pump (CP) equipped with a variable frequency drive (vfd) means to enable a selected fixed cross-flow (Q.sub.CP) in said batch CCD unit; a high pressure feed pump (HP) equipped with a variable frequency dive (vfd) means with its inlet line for feed and outlet line for pressurized feed to enable the a selected constant flux under variable pressure conditions irrespective of cross-flow; a line(s) for permeate release from said module(s) in said batch CCD unit; and a single PE means with its inlet line of pressurized concentrate brine, inlet line of feed, outlet line of decompressed concentrate brine, and outlet line of pressurized feed. Other features in FIG. 1(AB) include the followings: the connecting lines from said closed circuit line of said batch CCD unit to the inlet line of pressurized concentrate brine and to the outlet line of pressurized feed of said PE means; actuated valve means [V1, V2, and one-way check valve (CV)]; a flow/volume monitoring means on inlet line to HP (F.sub.HP) and on outlet line off CP (F.sub.CP); pressure monitoring means on inlet line (P.sub.in) to module(s) and on outlet line (P.sub.out) off module(s); and electric-conductivity monitoring means on permeate outlet line (E.sub.P), feed inlet line to HP (E.sub.HP), brine effluent line off PE (E.sub.S), and recycled concentrate in the closed circuit line (E.sub.CC).

(9) The RO skid design of said batch CCD unit in the preferred embodiment of the inventive system in FIG. 1(AB) is outlined with further details in FIG. 2(A-C). In said RO skids, the respective inlet and outlet lines of modules are connected in parallel to a single outlet line and a single inlet line which are part of said closed circuit line or concentrate recycling. Identical flow distribution to inlet(s) and off outlet(s) of module(s) in said RO skids under fixed low and variable pressure conditions implies an equivalent module performance, irrespective of the number of modules in the design provided that all the modules comprise of the same number of elements. Alignment of modules in said RO skids is possible in the vertical and/or horizontal configurations displayed in FIG. 2(A-C); wherein, FIG. 2A shows the vertical stacking of N modules of the NMEn configuration with their respective inlet and outlet tines connected in parallel; FIG. 20 shows the vertical stacking of N units, each comprises two horizontally inked modules, of the N(2MEn) configuration with respective inlet and outlet lines of all modules connected in parallel; and FIG. 3B shows the vertical stacking of N units, each comprises three horizontally linked modules, of the N(3MEn) configuration with respective inlet and outlet lines of all modules connected in parallel. The basic MEn unit in said configurations is of a module design comprising of a pressure vessel with n membrane elements (E) inside, with or without an additional empty volume inside pressure vessels created by spacers which is part of the free intrinsic volume of said module unit and that of the closed circuit of the entire system configuration—the free intrinsic volume of said module unit is an essential structural parameter which defines the fixed cycle duration during a batch CCD process under fixed flow and variable pressure conditions.

(10) The method of actuation of the preferred embodiment of the inventive system displayed in FIG. 1(AB) and FIG. 2(A-C) proceeds by a continuous two-mode consecutive sequential process under fixed flow and variable pressure conditions according to predetermined set-points of flux, module recovery (MR), and system recovery (R), or parameters derived from said set points such as fixed pressurized feed flow rate (Q.sub.HP) instead of flux, fixed cross-flow rate (Q.sub.CP) instead of MR [Q.sub.CP=Q.sub.HP*(100−MR)/MR], and maximum applied pressure (p.sub.max) instead of R. During said two-mode consecutive sequential process, engagement of batch CCD unit with PE means takes place only part of the time, to enable replacement of brine by fresh pressurized feed at the predefined desired system recovery from the intrinsic closed circuit volume (V.sub.i) of system. Flow through said PE means during engagement (Q.sub.PE) is the same as Q.sub.CP. CCD operation of unchanged flux, MR, and R in a fixed intrinsic volume (V.sub.i) proceeds by CCD cycles of constant time duration (V.sub.i/Q.sub.CP); wherein, recovery is a function of number of CCD cycles, or their cumulative batch sequence time intervals, with periodic engagement between said CCD and PE units to enable complete replacement of concentrate brine by fresh feed is of one CCD cycle duration (V.sub.i/Q.sub.CP) per a consecutive sequence. It should be pointed out again that the PE means are activated once per sequence for a single CCD cycle time duration (V.sub.i/Q.sub.CP), remain inactive during the rest of the time, and the frequency of PE means is function of recovery—declined frequency with increased recovery.

(11) Actuation of the preferred inventive system embodiment displayed in FIG. 1(AB) and FIG. 2(A-C) takes place by means of operational set-points (e.g., flux, MR and R or their derivatives) and online monitored data. The control-board actuation of said system relates to CCD and PE engagement/disengagement by the valve means. Inactive PE means is said system (FIG. 1A) implies an opened V1 and a closed V2 valve means; whereas, the activation of the PE means is achieved by the simultaneous closure of V1 and opening of V2 valve means in said system (FIG. 16). Accordingly, reaching the desired recovery will be manifested by a defined maximum applied pressure (p.sub.max) signal, or by a defined maximum electric conductivity signal of recycled concentrate (E.sub.max), and each said on-line monitored signals may apply to trigger PE engagement with the batch CCD unit for brine replacement with fresh feed without stopping desalination. The termination of the engagement may proceed after a single CCD cycle duration (V.sub.i/Q.sub.CP), since the fixed flow rates (HP and CP) in the system remain unchanged. An alternative engagement termination signal may relate to the monitored CP volume during engagement (ΣV.sub.CP) with a termination signal prompted when ΣV.sub.CP=V.sub.i.

(12) Apart from signals for valve means actuations, the monitoring means cited hereinabove in the preferred embodiment of the inventive system in FIG. 1(AB) also serve for the follow-up of the sequential CCD performance characteristics of pressure, flow rates, and electric conductivity which provide valuable information concerning of the development of fouling an/or scaling conditions in membranes and male function warnings specific system's components. It should also be pointed out that the reference to a single PE unit in FIG. (AB) and FIG. 2(A-C) is made for clarity and simplicity and that such a preferred embodiment of the inventive system may comprise of many such PE units of a simultaneous actuation mode as long as their respective inlet and outlet lines are connected in parallel according to the schematic drawing in FIG. 3.

(13) According to the preferred embodiment of the inventive system in FIG. 1(AB) and FIG. 2(A-C), the batch CCD unit operates continuously under fixed flow and variable pressure conditions while the PE unit operates periodically, once during each sequence and remains idle during the rest of the time. The frequency of PE actuation is defined by the number of identical CCD cycles (φ) required to reach a designated sequential recovery (R) with V.sub.i/Q.sub.CP expressing the active period per sequence of said PE unit and (φ−1)*(V.sub.i/Q.sub.CP) the non-active period of said unit with percent idle time expressed by 100*(1−1/φ). In CCD under fixed flow and variable pressure conditions, the term φ is defined by the selected R and MR set points, with sequential time period defined by R and the number of CCD cycles experienced during said sequence period determined by MR, or more specifically by Q.sub.CP, with a faster selected cross-flow manifested by a lower MR value, a larger number of CCD cycles (φ) per given R, and a shorter cycle period. The aforementioned dependencies in the context of the inventive system in FIG. 1(AB) and FIG. 2(A-C) of a typical brackish water source (2,000 ppm NaCl) at 20 lmh with 75%, 85%, and 95% recovery are illustrated, amongst other, in Example-1 (Table 1). The preferred embodiment of the inventive system in FIG. 1(AB) and FIG. 2(A-C) when applies to seawater CCD of 50% recovery at 13 lmh flux proceeds with few CCD cycles (e.g., 2-4) and a greater actuation frequency of the PE unit(s), with less idle time in between sequence.

(14) The CCD performance effectiveness under fixed flow and variable pressure conditions of the preferred embodiment of the inventive system in FIG. 1(AB) and FIG. 2(A-C) depends on a suitable selection of components with emphasis on the PE and CP units, valve means and an effective control board program. The said PE unit should be of a high hydraulic efficiency (>93%) not affected the changing pressure under constant flow conditions and of a fast starting response when engaged with the closed circuit of the batch CCD unit. Said engagement takes place when said batch CCD unit reaches its maximum applied pressure with an unchanged CP cross-flow rate (fixed Q.sub.CP), under which conditions a fast start of said PE unit is expected, pending a quick response of the actuated valve means in the system. The function of CP.sub.vdf in FIG. 1(AB) and FIG. 2(A-C) is to maintain a fixed cross-flow rate in said batch CCD unit and this implies enough power to overcome the module(s) pressure difference (Δp) when said batch CCD and PE units are disengaged as well as the to provide a pressure supplement (Δp.sub.PE) when both said units are engaged, where Δp.sub.PE is the pressure loss in said PE unit. The vfd means in said CP.sub.vdf should be sufficiently responsive to enable a near constant cross-flow during the engaged/disengaged modes in the inventive system.

(15) Another preferred embodiment of the inventive system in FIG. 4 describes the integration of two batch CCD units with the same pressure exchange means comprised of either one such unit (PE) or multitude of PE units (PEn) with their respective inlets and outlets connected in parallel. The engagement of the CCD units and PE means in said inventive system is enabled alternately, rather than simultaneously, through the valve means, while desalination is continued nonstop in both CCD units. The features in said batch CCD units, labeled RO-1 and RO-2, are same as already explained hereinabove for the preferred embodiment of the inventive method in FIG. 1(AB) and FIG. 2(A-C). Each batch CCD unit in FIG. 4 is autonomous and can be engaged alternately with said PE means for brine replacement by fresh feed through a concentrate line off its closed circuit line and valve means. In simple terms, PE means in of the preferred embodiment in FIG. 4 can be engaged with either RO-1 or with RO-2, one at a time, through their respective conducting lines and valves means, and remain idle when not engaged. Three operational modes are enabled by valve means actuation (opened closed positions) of the inventive system under review (FIG. 4) as followed: Continuous desalination while PE means are idle (Opened position.fwdarw.V11 and V21; Closed position.fwdarw.V12, V13, V22 and V23); Continuous desalination with PE means engaged with RO-2 (Opened position.fwdarw.V11, V22 and V23. Closed position.fwdarw.V21, V12 and V13); and Continuous desalination with PE means engaged with RO-1 (Opened position.fwdarw.V21, V12 and V13. Closed position.fwdarw.V11, V22 and V23). Valve means V13 and V23 can be replaced by one-way check valve means, since the outlet line from said PE means is always under a somewhat reduced pressure (2-3 bare) than that of the recycled concentrate inside said batch CCD units. The actuation mode of the inventive system displayed in FIG. 4 is that where RO-1 is disengaged and RO-2 engaged with the PE means.

(16) A single unique mode of operation of the preferred embodiment of the inventive system in FIG. 4 exists when both batch CCD units in the design are of identical configuration and operate identical two-cycle CCD consecutive sequences of same flux, module recovery (MR), recovery (R), sequence time duration (2*V.sub.i/Q.sub.CP), and cycle time duration (V.sub.i/Q.sub.CP). In this event, the inventive system in FIG. 4 is actuated with the PE means operated continuously, half the time with said RO-1 and half the time with said RO-2. Moreover, the entire conducting lines between the CCD units and pressure PE means in FIG. 4 remain under pressure, implying a small pressure difference during the actuation of the valve means in the system and the ability to achieve fast actuation of valves without damage. The monitoring means in the inventive system in FIG. 4, although not cited, are of the same type and located in the same respective positions as revealed for the single batch CCD unit in FIG. 1(AB).

(17) The inventive system in FIG. 4 for the simultaneous actuation of two batch CCD units with the same PE means can operate with one batch CCD unit with idle PE means when not engaged. This option, enabled by valve control means, implies the ability to stop one of the two batch CCD units in the system for maintenance and/or repair while the other is maintained operational.

(18) A modified design of the preferred embodiment of the inventive system in FIG. 4 is revealed in FIG. 5; wherein, a single high pressure pump (HP) without vfd means supplies a fixed flow of the fixed minimum pressure required by the batch CCD units, with pressure boosting inside the module(s) of RO-1 and RO-2 to enable a fixed permeation flow operation achieved by means of the respective booster pumps BP1.sub.vfd and BP2.sub.vfd, both equipped with vfd means to allow a fixed flow control. The monitoring means in the inventive system in FIG. 5, although not cited, are of the same type and located in the same respective positions as revealed for the single batch CCD unit in FIG. 1(AB).

(19) Systems according to the inventive method may comprise many batch CCD units which engage with the same PE means sequentially, one at a time, for concentrate brine replacement with feed. Inventive systems with many identical batch CCD units operated under the same conditions, will engage the PE means continuously when the cycle-number (φ) to reach a designated recovery (R) is the same as the number of said batch CCD units. In this case, the sequence time duration of each said batch unit is expressed by φ*V.sub.i/Q.sub.CP) with cycle time duration of V.sub.i/Q.sub.CP expressing the sequential periodic engagement with said PE means.

(20) It will be understood to the skilled in the art that the inventive systems of the inventive method pertain to integration between batch CCD unit(s) of fixed flow and variable pressure mode of operation and PE means to enable periodic concentrate brine replacement by feed in said batch CCD unit(s) without stopping desalination, and that the preferred embodiments of the inventive systems in FIG. 1(AB), FIG. 2(A-C), FIG. 3, FIG. 4 and FIG. 5 are schematic and simplified and are not to be regarded as limiting the invention but as several examples of many for the diverse implementation of the invention. In practice, systems according to the inventive method may comprise many additional lines, branches, valves, and other installations and devices as deemed necessary according to specific requirements while still remaining within the scope of the invention's claims.

(21) It will be understood to the skied in the art that means for pressurizing feed, boosting feed pressure, recycling of concentrate, pressure exchange, and flow manipulation are comprised of ordinary commercial components such as a pressure pump, a circulation pump, a booster pump, a pressure exchange device, and a valve device, or several such components that are applied simultaneously in parallel, or in line as appropriate. It is further understood that the referred monitoring means in FIG. 1(AB) are typical of al the inventive systems and that their signals essential for the actuation and control of specific components within said systems as well as for the entire systems. Noteworthy in particular in this context is the fixed flow operation of HP.sub.vfd and CP.sub.vfd in the batch CCD unit(s) of the inventive systems which is made possible through vid and flow monitoring means and that signals of such monitoring means apply to actuation of said valve means through a programmable control board whereby the entire operation is executed and controlled.

(22) It will be obvious to the skill in the art that the design of the inventive systems is not confined by the number of modules and/or element-number per module and/or the type of modules and elements in each said batch CCD unit, nor by the number of said batch CCD units and/or number of pressure exchange units per inventive system, and therefore, said inventive systems could apply also for large scale desalination of low energy and high recovery of salt water solutions including at the level of seawater.

(23) The inventive systems and methods pertain to the integration of batch CCD unit(s) with pressure exchange means through conducting lines with valve means into systems exemplified by the preferred embodiments in FIG. 1(AB), FIG. 2(A-C), FIG. 4 and FIG. 5 with monitoring and control means to enable continuous consecutive sequential CCD operation under fixed low and variable pressure conditions in compliance with predefined operational set-points of flux, module recovery and sequence recovery, which are independent of each other. The specified mode of operation is intended to enable continuous desalination of low energy high recovery also in inventive systems of large production capacity and high cost-effectiveness. Skilled in the art will recognize that the application of pressure exchange means with batch CCD unit(s) is non-obvious in the absence of any pressurized brine flow release during said CCD process as is case of conventional plug flow desalination techniques where pressure exchange means are being used continuously in a different mode.

(24) While the invention has been described hereinabove in respect to particular embodiments, it will be obvious to those versed in the art that changes and modifications may be made without departing form this invention in its broader aspects, therefore, the appended claims are to encompass within their scope al such changes and modifications as fall within the true spirit of the invention.

Example-I

(25) Seawater (35,000 ppm) CCD with operational set-points of 13 lmh flux, 33.3% module recovery (MR), and 50% recovery (R), according to the preferred embodiment of the inventive system in FIG. 4; wherein, each batch CCD unit comprises 42 module(s) of a specified number of elements per module of eight-section long pressure vessels. Both said CCD units in the system are of identical designs, operate with the same set-points, each executes a two-cycle consecutive sequences of 4.0 minute duration with a cycle period of 2.0 minute, and the PE means are operated continuously alternate every 2.0 minute from one CCD unit to the other, and thereby, allow a continuous desalination of both CCD units simultaneously at the same average set-point flux. In simple terms, the PE means in the design (FIG. 4) are operated nonstop and alternately engaged with each CCD unit for 2.0 minute duration. The various design and performance aspects of the exemplified system of the preferred embodiment are summarized in Table 1.

(26) TABLE-US-00001 TABLE 1 Illustration of the design and performance aspects of systems with 4MEn (n = 2-6) batch CCD unit configurations according to the preferred embodiment of the inventive system in FIG. 4, as applied for the desalination of seawater (35,000 ppm) with 50% recovery. Example Number #1 #2 #3 #4 #5 Membrane permeability coefficient - lmh/bar 1.798 1.798 1.798 1.798 1.798 Membrane salt diffusion coefficient - lmh 0.087 0.087 0.087 0.087 0.087 Module element-number 6 5 4 3 2 Module spacer-number 2 3 4 5 6 Module intrinsic volume - liter 164 180 197 213 229 Module-number per batch CCD unit 42 42 42 42 42 Number of batch CCD units per system 2 2 2 2 2 Sequence recovery (R) - % 50.0 50.0 50.0 50.0 50.0 Module recovery (MR) - % 33.3 33.3 33.3 33.3 33.3 av-Element recovery (AER) - % 6.5 7.8 9.6 12.6 18.3 av-Concentration Polarization factor (av-pf) 1.11 1.13 1.17 1.23 1.34 av-Flux, lmh 13 13 13 13 13 Cycle-number per CCD sequence 2.00 2.00 2.00 2.00 2.00 CCD sequence duration - min. 3.09 4.08 5.56 8.03 12.97 CCD cycle duration - min. 1.54 2.04 2.78 4.01 6.48 Sequence engagement of CCD batch unit - min. 1.54 2.04 2.78 4.01 6.48 Minimum applied pressure - bar 43.6 44.0 44.9 46.6 50.3 Maximum applied pressure - bar 55.5 56.1 57.3 59.7 64.6 average applied pressure - bar 49.5 50.1 51.1 53.1 57.4 HP-vfd efficiency - % 85 85 85 85 85 CP-vfd efficiency - % 75 75 75 75 75 Pressure exchange unit efficiency - % 95 95 95 95 95 average energy consumption - kWh/m.sup.3 1.831 1.803 1.805 1.853 1.990 average TDS of permeates - ppm 347 354 364 382 419 CCD batch unit production - m.sup.3/day 3,208 2,673 2,139 1,604 1,069 System production - m.sup.3/day 6,416 5,346 4,277 3,208 2,139

(27) Noteworthy features in Table 1: Inventive systems of MEn (2-6) module designs; a low energy consumption depending on module design [1.805-1.853 kWh/m.sup.3 for MEn (n=3-6), and 1.990 kWh/m.sup.3 for ME2]; permeate of 347.fwdarw.419 ppm TDS with salinity order manifesting increased concentration polarization of 1.11.fwdarw.1.34; fixed flux operation with production capacity manifesting the number of elements per module in the design; and maximum production capacity per system of two batch CCD 42*ME6 units (#1) of 6,416 m.sup.3/day (2*3,208 m3/day). The data of columns #4, #5 signify unadvisable operational conditions from the stand point of concentration polarization (≥1.20).

Example-II

(28) Salt water solution (2,000 ppm NaCl) batch CCD with operational set-points of 20 lmh flux; a selected module recovery (MR) manifesting a concentration polarization factor of 1.17; and a selected recovery (R) of 75%, or 85%, or 95%, according to the preferred embodiment of the inventive system in FIG. 1; wherein, said batch CCD unit comprises 42 modules of a specified number of elements per module [42MEn, n=4-6] made of eight-section long pressure vessel, and its operation proceeds by consecutive CCD sequences with periodic concentrate brine replacement by feed achieved by engagement with pressure exchange means for a single cycle duration; and thereafter, said pressure exchange means disengaged and remain idle until the next said engagement, with design and performance aspects said inventive systems summarized in Table 2.

(29) TABLE-US-00002 TABLE 2 Illustration of the design and performance aspects according to the preferred embodiment of the inventive system in FIG. 1 with batch CCD unit configuration of 42MEn (m = 3-6) as applied to the desalination of a salt water solution of 2,000 ppm NaCl with 75%, 85% and 95% recovery. Example Number #1.1 #1.2 #1.3 #2.1 #2.2 #2.3 #3.1 #3.2 #3.3 Membrane permeability coefficient - lmh/bar 4.985 4.985 4.985 4.985 4.985 4.985 4.985 4.985 4.985 Membrane salt diffusion coefficient - lmh 0.146 0.146 0.146 0.146 0.146 0.146 0.146 0.146 0.146 Module element-number 6 6 6 5 5 5 4 4 4 Module spacer-number 2 2 2 3 3 3 4 4 4 Module intrinsic volume - liter 164 164 164 180 180 180 197 197 197 Module-number per batch CCD unit 42 42 42 42 42 42 42 42 42 Sequence reovery (R) - % 75 85 95 75 85 95 75 85 95 Module recovyer (MR) - % 45.00 45.00 45.00 40.00 40.00 40.00 33.00 33.00 33.00 av-Element recovery (AER) - % 9.48 9.48 9.48 9.71 9.71 9.71 9.53 9.53 9.53 av-Concentration Polarization factor 1.17 1.17 1.17 1.17 1.17 1.17 1.17 1.17 1.17 av-Flux, lmh 20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0 Cycle-number per CCD sequence 3.67 6.93 23.22 4.50 8.50 28.50 6.09 11.51 38.58 CCD sequence duration - min. 6.02 11.38 38.14 7.95 15.02 50.34 10.84 20.48 68.65 CCD cycle dutation - min. 1.64 1.64 1.64 1.77 1.77 1.77 1.78 1.78 1.78 PE-CCD engagement per sequence - min. 1.64 1.64 1.64 1.77 1.77 1.77 1.78 1.78 1.78 PE idle time per sequence - min. 4.38 9.73 38.50 6.18 13.25 48.68 9.06 18.70 66.87 Minimum applied pressure - bar 7.5 7.5 7.5 7.2 7.2 7.2 6.9 6.9 6.9 Maximum applied pressure - bar 10.7 14.5 33.8 10.7 14.7 34.7 10.8 15.0 35.7 average applied pressure - bar 9.1 11.0 20.7 9.0 11.0 20.9 8.9 10.9 21.3 HP-vfd efficiency - % 80 80 80 80 80 80 80 80 80 CP-vfd efficiency - % 70 70 70 70 70 70 70 70 70 Pressure exchange unit efficiency - % 95 95 95 95 95 95 95 95 95 average energy consumption - kWh/m3 0.407 0.473 0.806 0.399 0.467 0.813 0.404 0.475 0.835 average TDS of permeates - ppm 38 56 143 39 57 148 39 58 152 CCD bath unit production - m3/day 4,935 4,935 4,935 4,113 4,113 4,113 3,290 3,290 3,290

(30) Noteworthy features in Table 2: Inventive systems of different module configuration (MEn; n=4-6); low energy consumption as function of recovery (0.400.fwdarw.0.835 kWh/m.sup.3 for 75% 495% recovery); permeates of 384*152 ppm TMS with salinity order manifesting increased recovery; and inventive systems of fixed operational flux, same concentration polarization factor (1.17), with permeate output proportional to the number of elements per module in the design of maximum production capacity (4,935 m.sup.3/cay) exemplified with 42ME6 units (#1.1, #1.2, and #1.3).

Benefits of Inventive Systems Over Prior Art

(31) 1. Large Scab, Low Energy, Cost-Effective SWRO-CCD Systems

(32) Low cost continuous seawater closed circuit desalination under fixed flow and variable pressure conditions of low energy consumption and large production capacity is taught hereinabove by the periodic engagement of batch CCD unit(s) with pressure exchange means to enable concentrate brine replacement by feed and thereby, allow a batch process continued on a consecutive sequential basis. The inventive method overcomes the limitations of large intrinsic volume requirements and complex conduit lines and valve means of PCT/IL2002/000636 with two alternating side containers and of PCT/IL2004/000748 with a single side container, both of confined CCD production capacity and low cost-effectiveness. The preferred embodiment of the inventive systems in FIG. 1 and FIG. 2 are suitable for large scale consecutive sequential CCD of seawater by a process involving active/inactive PE means; whereas, the preferred embodiment of the inventive systems in FIG. 4 and FIG. 5, teach the integration of two batch CCD units with the same PE means of a continuous actuation mode with alternating engagement to each said batch CCD unit for the same time duration—systems suitable for large scale seawater desalination of low energy high-cost effectiveness.

(33) Example #1 in Table 1 illustrates the performance a single batch CCD unit of 42ME6 configuration for 3,208 m.sup.3/day desalinated seawater of 50% recovery with energy consumption of 1.831 kW/m.sup.3 and permeates' quality of 347 ppm average TDS; and an integrated inventive system two batch CCD units with the same PE means of 2[42ME6] configuration for double production (6,416 m.sup.3/day) under the same conditions.

(34) 2. Large Scale, High Recovery, Cost-Effective BWRO-CCD Systems of Declined Fouling Propensity

(35) While PCT/IL2002/000636 with two alternating side containers and of PCT/IL2004/000748 with a single side container can apply to low energy higher recovery desalination of brackish water desalination with unchanged membranes performance, said techniques are confined to small scale production of low cost-effectiveness due to their large intrinsic volume requirements and complex conduit lines and valve means. PCT/IL2005/000670 eliminates the needs for a side container of large intrinsic volume and extensive valve means making this technology highly cost effective for brackish water desalination of low energy and high recovery by a two-step consecutive sequential process with CCD under fixed flow and variable pressure conditions experienced most of the time (>85%) with brief periodic PFD steps of low flux and recovery to enable brine replacement by feed, and the two-step process implies frequent changes of membrane performance. The inventive systems in FIG. 1, FIG. 2, FIG. 4 and FIG. 5 teach large scale consecutive sequential CCD of brackish water of high recovery and low energy with unchanged membrane performance as previously taught by PCT/IL2002/000636 and PCT/IL2004/000748, but without intrinsic volume imitations on large scale production. The advantage of present inventive systems over PCT/IL2005/0006170 arises from thei steady unchanged membrane performance during the course of desalination, including when brine concentrate is replaced with fresh feed.

(36) In reference to large scale desalination prospects of brackish water by the inventive systems, noteworthy are the projected performance results in Examples #1.1 (75%; 0.407 kWh/m.sup.3; 38 ppm TDS; 4,935 m.sup.3/day), #1.2 (85%; 0.473 kWh/m.sup.3; 56 ppm TDS; 4.935 m.sup.3/day), and #1.3 (95%; 0.806 kWh/m.sup.3; 143 ppm TDS; 4,935 m.sup.3/day) of Table 2 as applied to a 2,000 ppm NaCl feed source and a single batch CCD unit of 42ME6 configuration according to the preferred embodiment of the inventive systems in FIG. 1 and FIG. 2. Twice the production capacity (9.870 m.sup.3/day) is made possible when two said batch CCD units of same configurations are operated continuously and simultaneously with the same PE means according the preferred embodiment of the inventive systems in FIG. 4 and FIG. 5. The same conceptual design can be expanded to include 3 said batch CCD units for a system of 14,805.sup.3/day, 4 said batch CCD units for a system of 19.740.sup.3/day, and inventive systems alike.